The invention relates to a method for operating a control apparatus having a programmable memory unit for storing data and programs for the operation of the control apparatus.
A method of this kind is disclosed, for example, in DE 43 32 499 A1. The control apparatus, which is described in this publication, is a motor vehicle control apparatus which is equipped with programmable memory units in the form of flash EPROMs. More precisely, these memory units are erasable non-volatile memory units and store data and programs for the operation of the apparatus.
The provision of a programmable memory unit as a memory unit for storing data and programs for the operation of the control apparatus has proven to be advantageous because, in this way, the operation of the control apparatus can be permanently changed at any time in a simple manner and this is very significant especially for errors in the storage data and programs which errors were initially not recognized or for individual customer desires.
The use of flash EPROMs as programmable memory units has acquired increasing significance because they unite the advantages of a normal EPROM (high memory cell density in a tight space) and an EEPROM (electric and therefore simple and comfortable erasure of the memory content).
An external programming apparatus (for example, in the form of a personal computer) is connected to the control apparatus for initial programming, that is, erasure and/or overwriting of the flash EPROMs (preferably in dependence upon motor vehicle type in the motor vehicle manufacturing facility) or for a later reprogramming of the same (at the customer service facility for eliminating errors or according to individual customer desires). With a programming apparatus of this kind, the execution of control programs, which are stored in the control apparatus for erasing and/or overwriting of data in the flash EPROM is initiated and, if required, the data, which is newly stored, is made available.
A programmability of the memory unit of this kind which is simple and rapid to execute for storing data and programs for the operation of the control apparatus opens the possibility that the control apparatus is very flexible and, at the same time, can be adapted simply and rapidly to the particular situation.
On the other hand, a certain danger is associated with the possibility of overwriting or erasing the content of the memory unit because changes of the memory content can under circumstances lead to a considerable safety risk. This is especially so for changes which result because of disturbances or defective programming.
For this reason, it is, inter alia, necessary to eliminate as quickly as possible disturbances in the control apparatus and/or program apparatus. The search for the cause of a supposed disturbance is, however, only purposeful when it is certain that the change in the content of the memory is actually caused by a disturbance.
The present invention is therefore based on the object of seeking suitable measures which permit the determination of the cause for an improper content of the programmable memory unit.
According to the invention, the data documenting the programming operation are stored together with the programming of the programmable memory unit.
By correspondingly selecting the data, which document each programming operation, and storing the same in a non-volatile memory, more or less detailed statements can be made at any time from these data as to reprogramming of the programmable memory unit which has, possibly, been undertaken.
The more complete the data selected for documentation of the respective programming operations, the more precise can a later. reconstruction of the affected programming operation be effected.
The data, which are selected for documentation of each program operation, can, for example, contain information as to:
the time point, the sequence, the duration and/or the success of each programming operation;
the position (within the memory unit), the extent, the type (erasure and/or overwriting) and/or the content (for example, check sums of newly written data and the like) for each undertaken change; and/or
the program apparatus which initiated the particular programming operation.
By evaluating information of this kind, it can be determined whether and to what extent particular regions of the programmable memory unit were subjected to data changes because of reprogramming operations.
The control apparatus and/or the programming apparatus suffer a disturbance which should be corrected when a data change, which is to be investigated, lies outside of ranges, which are changed by programming, or if the change is one which was not made by reprogramming.
In this way, it is possible to reliably determine the cause for an improper content of the programmable memory unit.
The determination of the cause is carried out in accordance with a fixed scheme which permits an automatic self test to be carried out for disturbances which are to be corrected, as needed.
Furthermore, and in addition to the reliable recognition of disturbances, the method of the invention makes it possible to determine whether, for an undertaken reprogramming of the programmable memory unit, a proper programming was performed by an authorized facility or a programming (inadvertent or deliberate misuse) was made by an unauthorized person.
Advantageous further embodiments of the invention are the subject matter of the dependent patent claims.
The invention is explained in greater detail in the following with reference to an embodiment while making reference to the drawing.
The FIGURE shows a control apparatus connected to an external programming apparatus which permits the method according to the invention to be carried out.
The explanation which follows relates to a method for operating a control apparatus and especially a control apparatus for controlling, for example, the engine, the transmission or the brakes, et cetera of a motor vehicle, that is, a motor vehicle control apparatus.
The control apparatus includes memory units, or more precisely erasable non-volatile memory units in the form of flash EPROMs having the special advantages for this area of application as already mentioned herein. These memory units are for storing data and programs for the operation of the control apparatus.
The programming of the memory units takes place via an external programming apparatus which can, for example, be connected to the motor vehicle control apparatus via a serial interface.
However, the present invention is not limited to the programming of flash EPROMs in motor vehicle control apparatus while using an external programming apparatus. The invention is rather everywhere applicable where a storage unit of a control apparatus is to be programmed via a programming arrangement.